Passed a key to a girl (3)
I believe the answer is:
did
'passed' is the definition.
(doing is a kind of passing)
'a key to a girl' is the wordplay.
'a key' becomes 'd' (I've seen this in other clues**).
'to a' is a charade indicator (letters next to each other) (I've seen this in other clues).
'girl' becomes 'di'.
'd' after 'di' is 'DID'.
(Other definitions for did that I've seen before include "Executed!" , "Carried out, performed" , "was satisfactory" , "Swindled" , "Performed an action" .)